Balancing putty and balancing compounds that include an epoxy resin and a curing agent and which are designed for application to a rotary part, such as a rotor of a motor, in order to provide for well-balanced rotation are prevalent in the prior art. For example, U. S. Pat. No. 5,008,309 issued to Ibe et al. describes a balancing putty for balancing the rotation of a rotary part which includes an epoxy resin, a curing agent capable of curing the epoxy when it is heated to a temperature of 60 degrees C. or higher, a first inorganic filler, and a second inorganic filler. Further, another patent issued to Ibe et al., namely U.S. Pat. No. 5,201,248, discloses a one-pack type liquid epoxy resin composition for balancing rotators which comprises an epoxy resin, a curing agent, a curing accelerator, an inorganic filler, and a thixotropic agent as its main components.
U.S. Pat. No. 5,384,339 issued to Starkey also discloses an epoxy based balancing compound. This patent describes a balancing compound having an epoxy resin, a photo initiator for curing the resin at an ambient temperature upon the application of ultraviolet light, and a filler to give the compound a certain specific gravity. Another patent, U.S. Pat. No. 5,516,813, also issued to Starkey describes a similar epoxy based ultraviolet light curable balancing composition which includes an epoxy resin, a photo initiator for curing the resin at ambient temperatures upon applying ultraviolet light, and a filler comprising ultraviolet light transparent quartz in certain amounts by weight to give the composition a specific gravity above 1.1.
However, the present invention relates even closer to U.S. Pat. No. 3,939,020 issued to Caramanian et al. Pat. No. 3,939,020 describes a method for balancing a rotor which uses an epoxy resin balancing composition that includes an epoxy resin, a fibrous inorganic material, a powdered weighting material, a reactive polyamide, and a catalyst and a diluent. Further, another patent issued to John Caramanian, namely U.S. Pat. No. 4,083,735, discloses a method and composition for dynamically balancing rotors which includes the application of a balancing composition that comprises essentially the same elements as Pat. No. 3,939,020 with the exception that the elements exist in different concentrations by percent weight, there is no diluent, and the resulting composition must have a specific gravity of at least 3.0. In both Caramanian patent references, the epoxy resin is an epichlorhydrin-bisphenol A epoxy resin and the powdered weighting material is selected from either powdered zinc or powdered barium sulfate.
As described in the above-referenced Caramanian patents, dynamic balancing equipment is used to rotate the rotator in order to determine the required amount and placement position of the balancing composition in order to balance the rotor. Next, the determined amount of balancing composition is applied to the determined position of the rotor such that the balancing composition adheres to the rotor. The rotor is then rotated and dynamically tested to determine correct balancing. If the balancing is incorrect, either a portion of the balancing composition is removed from the rotor or balancing composition is added to the rotor in order to balance the rotor.
The present invention is directed to improved chemical compositions for dynamic balancing which include an epoxy resin, powdered barium sulfate as a weighting material, iron oxide pigment or other color pigments, and an expanded aramid fiber. Variations of this improved chemical composition are also contemplated by this invention which comprise the inclusion of one or more additional curing agents, specifically a polyamide, a polyamine, or a combination thereof, and/or additional pigments.
The improved compositions of the present invention result in improved characteristic properties over the compositions currently existing in the prior art, as well as certain procedural and formulational advantages which relate to the improved compositions. Some of those improved characteristics and advantages are as follows:
(i) The improved balancing compositions of the present invention are easier to mix. PA1 (ii) The improved balancing compositions of the present invention eliminate asbestos, zinc powder, calcium silicate, and the high boiling aromatic which were previously used with the existing prior art making them more user friendly and environmentally safe. PA1 (iii) The improved balancing compositions of the present invention eliminate the need for overlaying the balancing compound in an armature with pressure sensitive tapes, or other tapes, to hold the balancing compound in place. PA1 (iv) The improved balancing compositions of the present invention are applied after the armatures are varnish dipped, in contrast to before the armatures are varnish dipped as was the case with the existing prior art compounds. In that varnish dipping throws off the balance of the rotor, applying the balancing composition after varnish dipping provides for improved, more concise balancing. PA1 (v) The facile mixing of the improved balancing compositions of the present invention make it both feasible and possible for these compositions to be used in specially designed mixing and dispensing equipment, thereby opening up new markets in the balancing field previously not accessible to a hand mixed, hand applied product. PA1 (vi) The improved balancing compositions of the present invention may be processed through a machine that heats the composition, or not, mixes the composition, cools the composition, or not, and then dispenses the composition in preset or predetermined amounts or shots. Further, this type of mixing/dispensing machine may be coupled to a dynamic balancing machine, which determines the required amount and placement position of the balancing composition, so that the dispensed shots are of an amount equal to, or the same as, the amount previously determined by the dynamic balancing machine. PA1 (vii) Because of their improved mixing qualities, the improved balancing compositions of the present invention may be dispensed through either manual or power actuated, high performance, plural component cartridge or plural component dispensing systems. PA1 (viii) The improved balancing compositions of the present invention drastically reduce the time required for balancing. The new compositions may eliminate the necessity of trial balance, eliminate many weight location problems, and can be rotated and balanced in the uncured state. Some embodiments of the composition also cure much more quickly than those compositions disclosed in the prior art thereby reducing the waiting time required for motor assembly. PA1 (ix) The improved balancing compositions of the present invention are non-conductive and thereby eliminate the possibility of electrical shorting due to balancing.